The compounds of formula (I), as defined below, can be useful as starting material for the construction compounds having a more complex skeletons, such as 4-hydroxy-2,5-dimethyl-3(2H)-furanone (known as Furaneol®, Trademark of Firmenich SA).
Various processes for the preparation of compounds of formula (I) have been reported, for example Briggs et al, J. Chem. Soc. Perkin. Trans. I, 1985, 795 relates to a multistep synthesis of the 3,4-dihydroxyhexane-2,5-dione starting from the tartaric acid, or Bassignani et al, J. Org. Chem., 1978, 43, 4245 relates to the synthesis of the 3,4-dihydroxyhexane-2,5-dione by oxidizing the expensive 2,5-dimethylfuran with the toxic and expensive KClO3/OsO4 system. Another reported method to synthesize compounds (I) is the reductive dimerisation of glyoxals promoted by various methods (for instance see EP 368211 or Büchi et al, J. Org. Chem., 1973, 38, 123).
The above-mentioned methods of preparation are in general quite long and expensive or imply the use of a large excess of heavy metal which implies problems of purification of the final product and of waste treatment.
To the best of our knowledge, in the prior art there is no report of an aldol condensation giving a direct access to compounds of formula (I).